As for the digital image system, that is a system which can convert analog image signals into digital image signals so that the digital image signals can be stored in an image memory, and which, if necessary, can reproduce it, such as digital VTR, image filing system, digital television and the like.
Generally the frames reproduced through the television system are successively scanned 30 times per second and one frame is scanned by dividing into two field scannings, thereby causing an effect which appears as if 60 frames are scanned. That is, in case of the television system in Korea, one frame consists of 525 scanning horizontal lines, of which odd horizontal scanning lines and even horizontal scanning lines are separated from each other, each of which is called one field, and one frame is completed by both fields to be scanned separately, one by one.
The interlaced scanning method as described above is also employed in a video camera producing the image signal. Therefore, the image signals consisting of one frame are not associated with the transient images, but the image signals corresponding to each one of the scanning lines are associated with the images having a time interval therebetween each other. Accordingly, the image signals constituting one frame do not constitute simultaneous instant pictures such as photographs but constitute continuously changing. Therefore, if one frame of scenes, in which the object to be pictured is moving, is repeatedly seen, it is found that the flicker phenomenon, in which the frame fluctuates or flickers, is caused by the time difference in one still picture frame constituted by two fields.
FIG. 1 is a block diagram showing a conventional digital image processing system, in which an A/D converter 2 receives analog video signals to converted into digital signals at a predetermined sampling frequency from a controller 1. Then, controller 1 applies the address signals and the write control signals to an image memory 3 to store the digital signals in image memory 3, and in case of reproduction of them applies the read control signals and the address signals thereto. Since in image memory 3 one frame or one field of picture data is stored, upon reproduction of the still picture frame the stored picture data are reproduced as analog videp signal through a D/A converter 4 by the read control of controller means 1.
Therefore, the conventional system has problems in which, upon reproduction of the still picture frame, if one field of picture data is stored in image memory 3, then the number of horizontal scanning lines constituting the picture frame is reduced by half so that the picture frame is rough and its quality deteriorates by repeatedly reproducing a picture frame with only one field (odd or even horizontal scanning lines), and if one frame of picture data is stored in image memory 3, then the flicker phenomenon in which the picture frame fluctuates or flickers, is caused by the time difference between two fields constituting one picture frame as described above.